I assume, Kentishbear, that you're a fella'. It's also likely that you're sitting down, while wearing trousers.
Based upon those assumptions, the crotch of your trousers will have risen up when you sat down, pushing your scrotum to one side. If you were wearing a professionally-tailored pair of trousers they'd have been made with slightly more free space to one side of the crotch, in order to comfortably accommodate your scrotum. The side to which your balls naturally fall is euphemistically described as the side which you dress to (or from).
Chris